Lights off: How artificial light at night might cause depression

Chronic exposure to dim light at night – such as a TV or computer screen -- might lead to depression, suggests a new study in animals.

The researchers at Ohio State University based their study on hamsters, but they say the rodents’ behavior may shed light on the rising rate of depression in humans.

In the study, hamsters that were exposed to dim light at night showed less activity during the day and greater depressive symptoms than hamsters that spent eight hours a day in total darkness. For the animals, drinking less sugar water counted as a depressive symptom.

“The results we found in hamsters are consistent with what we know about depression in humans,” said Tracy Bedrosian, the study’s lead author and a doctoral student of neuroscience at OSU.

However, when the depressed hamsters returned to a normal light-dark cycle for two weeks, their activity level and behavior returned to normal.

“The good news is that people who stay up late in front of the television and computer may be able to undo some of the harmful effects just by going back to a regular light-dark cycle and minimizing their exposure to artificial light at night,” Bedrosian said. “That’s what the results we found in hamsters would suggest.”

The researchers also studied changes in the hamsters’ brains and found the animals that lived in dim light increased expression of a gene that produces the protein tumor necrosis factor. It is part of a family of proteins that cause inflammation to fight infection. However, inflammation can be damaging if it is constant, the researchers said.